ALLOY CHEMISTRY OF POROUS MATERIALS: OPTIMIZATION OF ALLOY CHEMISTRY FOR POROUS MATERIALS

In solidified metals gas porosity usually lessens the mechanical properties and is therefore unwanted in the end product. A new method called GASAR has been developed in Dnepropetrovsk Metallurgical Institute in Ukraine for producing materials with controlled porosity which have a wide variety of uses. By directly solidifying solid-hydrogen gas eutectics under high pressure, the concentration, distribution, size and geometry of the bubbles are manipulated by varying different process variables. The nucleation of the bubbles as gaseous hydrogen bubbles is the initial stage of the process. The present work investigates the nucleation mechanism and different ways to manipulate the same. A theoretical study has identified effective heterogeneous nucleation sites. Evaluations of the thermodynamic limits set by hydrogen solubility and its dependence on temperature and pressure are given. Directions for future work are indicated.